Peridomestic Lyme Disease Prevention Results of a Population-Based Case–Control Study Neeta P. Connally, PhD, Amanda J. Durante, PhD, Kimberly M. Yousey-Hindes, MPH, James I. Meek, MPH, Randall S. Nelson, DVM, Robert Heimer, PhD Background: Peridomestic Lyme disease–prevention initiatives promote personal protection, landscape modification, and chemical control. Purpose: A 32-month prospective age- and neighborhood-matched case– control study was con- ducted in Connecticut to evaluate the effects of peridomestic prevention measures on risk of Lyme disease. Methods: The study was conducted in 24 disease-endemic Connecticut communities from 2005 to 2007. Subjects were interviewed by telephone using a questionnaire designed to elicit disease-prevention measures during the month prior to the case onset of erythema migrans. Data were analyzed in 2008 by conditional logistic regression. Potential confound- ers, such as occupational/recreational exposures, were examined. Results: Between April 2005 and November 2007, interviews were conducted with 364 participants with Lyme disease, and 349 (96%) were matched with a suitable control. Checking for ticks within 36 hours of spending time in the yard at home was protective against Lyme disease (OR0.55; 95% CI0.32, 0.94). Bathing within 2 hours after spending time in the yard was also protective (OR0.42; 95% CI0.23, 0.78). Fencing of any type or height in the yard, whether it was contiguous or not, was protective (OR0.54; 95% CI0.33, 0.90). No other landscape modifications or features were significantly protective against Lyme disease. Conclusions: The results of this study suggest that practical activities such as checking for ticks and bathing after spending time in the yard may reduce the risk of Lyme disease in regions where peridomestic risk is high. Fencing did appear to protect against infection, but the mechanism of its protection is unclear. (Am J Prev Med 2009;37(3):201–206) © 2009 American Journal of Preventive Medicine Introduction T he highest risk for Lyme disease in the north- eastern U.S. occurs in the peridomestic environ- ment. 1–3 Efforts to prevent infection, in the absence of a vaccine, have focused primarily on pre- venting exposure to the tick vector Ixodes scapularis (commonly known as blacklegged ticks or deer ticks). Recommended peridomestic prevention measures pro- mote three strategies: personal protection, landscape intervention, and chemical control. 4 Personal protective measures include performing tick checks (i.e., inspecting body parts for ticks) and wearing protective clothing. Landscape interventions that seek to create an inhospitable environment for ticks and their hosts, while maintaining a safe zone for recreation, include creating a dry barrier of gravel or mulch between lawn and woods or installing deer- exclusion fencing. Chemical control measures include spraying acaricide to reduce the number of ticks in the yard at home. Several studies have identified a number of perido- mestic risk factors for Lyme disease. 2,5–11 However, few have examined the effectiveness of recommended Lyme disease–prevention measures, and these have produced conflicting results. One study 8 showed no significant differences in personal protective measures taken by Lyme disease cases versus their age-matched controls. In contrast, another study 10 found that people who applied repellent before going outdoors or rou- tinely checked for ticks while outdoors were less likely to get Lyme disease. However, checking for ticks after coming in from being outdoors was not shown to be protective against Lyme disease. Data from another study 12 indicated that wearing protective clothing or repellent was more commonly practiced among people who did not have Lyme disease. Although chemical From the Connecticut Emerging Infections Program (Connally, Yousey-Hindes, Meek, Heimer), and the Yale Center for Public Health Preparedness (Durante), Yale School of Public Health, New Haven; and the State of Connecticut Department of Public Health (Nelson), Hartford, Connecticut Address correspondence and reprint requests to: Neeta P. Connally, PhD, Connecticut Emerging Infections Program, One Church Street, 7th Floor, New Haven CT 06510. E-mail: neeta.connally@yale.edu. 201 Am J Prev Med 2009;37(3) 0749-3797/09/$–see front matter © 2009 American Journal of Preventive Medicine • Published by Elsevier Inc. doi:10.1016/j.amepre.2009.04.026